The proposed investigation is directed toward defining the structure of the growth hormone and prolactin gene family and the mechanisms by which steroid and polypeptide hormones regulate their expression. This will be achieved by systematically analyzing questions concerning the structure and synthesis of their RNA products and the relationship these bear to the genomic DNA template. We will determine the boundaries of transcription and the modes by which the primary transcript is processed to yield mature mRNA. This will provide criteria for the development of faithful in vitro or allogenic systems of expression in which cloned genes will be reintroduced into mammalian cells. This will ultimately allow us to isolate and characterie hormonally inducible control elements.